Shatterproof lamination and method of manufacture



350-397 SR D d n OF?V Search Room Aug. 22, 1944. E. H. LAND. n 2,356,252

SHATTERPROOF LAIIINATION AND METHOD OF MANUFACTURE Filed nee. 2e, 1938 /f//f/f/ /l INVENTOR. 61am' Agn-c ATTORNEYS Search lRoom Patented Aug. 22, 194A f UNITED STATES PATENT OFFICE SHATTERPROOF LAMINATION AND METHOD OF MANUFACTURE Edwin H. Land, Boston, Mass., assigner to Polaroid Corporation, Dover, Del., a corporation of Delaware Application December 28, 1938, Serial No. 248,027

12 Claims. (Cl. 88-65) An object of the invention is to provide a lampolarizing flhns have been employed, difficulties ination of the shatterproof or safety glass type have arisen by reason of the disorientation of for use in headlight lenses, viewing visors, sunthe polarizing crystals within the film as a reglasses, scientific instruments and the like, and sult of .stress exerted on the film by movement comprising a polarizing film and means for suitthereagainst of the adhesive layer employed in ably cementing the film between two sheets of the lamination. This movement arises from the glass or the like. pressure exerted upon the lamination in its for- Other objects of the invention are to provide mation. l a lamination of the character described in which With the use of exceedingly thin films of lightthe polarizing nlm is in direct contact with one polarizing material of the type heretofore deof the glass sheets and in which a layer of an l5 scribed, this displacement of the polarizing axes adhesive is introduced between the film and the of the crystals is aggravated. Even if such films other of the glass sheets; to provide such a lamcould be readily handled it would be highly deination in which the polarizing film is protected sirable to protect them from contact with the from the adhesive layer by a barrier element, for adhesive layers Comprising the lamination t0 example by a thin film of regenerated cellulose; prevent flow of the adhesive during Compression to provide such a lamination in which edge-sealof the lamination from affecting the polarizing ing is effected to protect the polarizing film and crystals. the barrier layer from contact with moisture. As the said copending application points out,

A still further object of the invention is to the polarizing layers there described may be readprovide a process for the manufacture of a lamily formed on or transferred to thin supporting ination of the character described. sheets, for example sheets of regenerated cellu- The invention accordingly comprises the sevlose or the like. Cellophane, which has been eral steps and the relation of one or more of such freed from glycerine, is particularly adapted for steps with respect to each of the others, and the the purpose of this invention, and is a preferred article possessing the features, properties, and support for the polarizing film. It is to be unthe relation of elements which are exemplified derstood, ho'wever, that other relatively thin, in the following detailed disclosure, and the scope transparent supporting media may be employed. of the application of which will be indicated in The drawing illustrates a preferred form ofv the claims. the lamination of the present invention. It com- For a^fuller understanding of the nature and prises two preferably rigid, transparent supportobjects of the invention, reference should be had ing sheets I0 which may preferably be of glass, to the accompanying drawing, which is a seca polarizing film I2 in direct contact with one of tional view, greatly` enlarged and somewhat disthe glass sheets I0, a backing I4 for the film I2, torted, of a lamination embodying the invenwhich may preferably be a sheet of Cellophane non, 40 free from glycerine to which the film has beenv There has been developed an exceedingly efilmounted prior to its assemblage in the laminacient light-polarizing film which is described in tion, and a layer of an adhesive I6, which may greater detail in the copendlng applicaton of Edcomprise a polymerized incomplete vinyl acetal win H. Land, Serial No. 233,379, filed October 5, resin and which may be plasticized with any of 19.38, now Patent No. 2,289,713, issued July 14, the commercial plasticizers used with such a res- 1942. This film comprises a highly concentrated in, or with castor oil. The adhesive, for examsuspension of minute, needle-shaped crystals of Die, may be the material sold commercially as a light-polarizing material, such for example as VinaL Other materials may be used as the a herapathite-like material in a light-transmitadhesive layer, for example, methyl acrylate, ting suspending medium such for example as a methyl methacrylate, vinyl acetate, a polyisobupolymerized incomplete vinyl acetal resin. The tylene such as the material sold as Victanex polarizing films of this type may be exceedingly High Molecular Weight, a product of Advance thin. for example they may not exceed .0003 of Solvents and Chemical Corp., or the like. an inch. They are fragile and are not easily In preparing the lamination the polarizing film handled unless fixed to some supporting sheet. is first formed on or transferred to the barrier They are, however, exceedingly efficient, and it is highly desirable that they be employed in laminations of the type herein disclosed.

In effecting laminations in the past in which membrane of cellophane or other similar material in the manner described in the said copending application. This assemblage is then placed on the glass plate with the polarizing film in direct contact with the plate. It may, for example, be applied to the glass sheet by passing a'heated roll over the assemblage and pressing it against the glass. If desired a plasticizer-lubricant may be employed between the polarizing film and the glass to plasticize the film and thus facilitate its adhesion and to lubricate the interface between the film and glass and thus to eliminate air and other foreign matter. An example of a substance suitable for this purpose is a chlorinated diphenyl such as that sold under the trade name Aroclor 1248. A layer of the adhesive is then placed upon the top of the Cellophane or other barrier film and the second glass plate then placed on the adhesive layer. The entire assemblage is then subjected to suitable temperature and pressure, and a permanent, substantially shatterproof bond effected. The pressure employed may be such as a cause the adhesive layer to flow. The Cellophane membrane acts to protect the polarizing layer from the flowing adhesive, and hence the heavy plastic is prevented from disorienting the polarizing crystals in the polarizing film. The Cellophane or other barrier layer also functions to keep the plasticizer in the plastic layer from contact with and penetrating the polarizing film. This is important in maintaining the highest efficiency of the polarizing layer.

Where the polarizing film comprises a suspension of polarizing crystals in a polymerlzed incomplete vinyl acetal resin, and this is a preferred form of the invention, the polarizing film adheres directly and permanently to the adjacent glass support. The film should preferably contain so little plasticizer that it does not ow at the temperature and pressure used in forming the lamination.

Under certain circumstances, as is shown in the drawing, the glass supports may extend beyond the edges of the polarizing and barrier films, and the heavy adhesive layer may extend from one to the other of the glass supporting sheets, thus effectively edge-sealing the polarizing film.

Since certain changes in carrying out the above process, and certain modifications in the article which embody the invention may be made without departing from its scope, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In combination, a transparent, rigid support, a polarizing film aflixed thereto, a transparent barrier film affixed to the opposite face of said polarizing film, and a relatlvelyheavy adhesive layer afllxed to and positioned intermediate said barrier layer and a second transparent, rigid support, said polarizing film adhering directly and permanently to said first-men-v tioned rigid support, all of the elements of said combination being permanently bonded together to provide a substantially shatterproof structure.

2. In combination, a transparent, rigid support, a polarizing film afilxed thereto, a transparent barrier nlm aixed to the opposite face of said polarizing film, and a relatively heavy adhesive layer aiiixed to and positioned intermediate said -barrier layer and a second transparent, rigid support, said rigid supports comprising glass sheets, said polarizing film adhering directly and permanently to said first-mentioned rigid support, all of the elements of said combination being permanently bonded together to provide a substantially shatterproof structure.

3. In combination, a transparent, rigid support, a polarizing film affixed thereto, a transparent barrier film afllxed to the opposite face of said polarizing film, and a relatively heavy adhesive layer alxed to and positioned intermediate said barrier layer and a second transparent, rigid support, said heavy adhesive layer Aencompassing said barrier film and said polariz-l ing film to provide an edge-sealed shatterproof lamination, said light-polarizing film adhering directly and permanently to said first-mentioned rigid support and being of smaller area than said heavy adhesive layer.

4. In combination, a transparent, rigid support, a polarizing film affixed thereto, a transparent barrier film affixed to the opposite face of said polarizing film, and a relatively heavy adhesive layer amxed to and positioned intermediate said barrier layer and a second transparent, rigid support. said barrier film being adapted to prevent plasticizer in said heavy adhesive layer from coming in contact with said polarizing film, said polarizing film adhering directly and permanently to said first-mentioned rigid support, all of the elements of said combination being permanently bonded together to provide a substantially shatterproof structure.

5. In combination, a transparent, rigid support, a polarizing film comprising a suspension of oriented polarizing crystals in a medium comprising a polymerized, incomplete vinyl acetal resin amxed thereto, a transparent barrier film aixed to the opposite face of said polarizing film, and a relatively heavy adhesive layer ailixed to and positioned intermediate said barrier layer and a second transparent, rigid support, said polarizing film adhering directly and permanently to said first-mentioned rigid support, all of the elements of said combination being permanently bonded together to provide a substantially shatterproof structure.

6. In combination, a transparent, rigid support, a polarizing film affixed thereto, a transparent barrier film comprising a sheet of regenerated cellulose aflixed to the opposite face of said polarizing film, and a relatively heavy adhesive layer affixed to and positioned intermediate said barrier layer and a second transparent, rigid support, said polarizing film adhering directly and permanently to said first-mentioned rigid support, all of the elements of said combination being permanently bonded together to provide a substantially shatterproof structure.

7. In combination, a transparent, rigid support, a polarizing lm affixed thereto, a transparent barrier film comprising a sheet of glycerine-free, regenerated cellulose affixed to the opposite face of said polarizing film, and a relatively heavy adhesive layer afllxed to and positioned intermediate said barrier layer and a second transparent, rigid support, said polarizing film adhering directly and permanently to said firstmentioned risid support, all of the elements ot w Uniti-a@ Search Room said combination being permanently bonded together to provide a substantially shatterproof structure.

8. In combination, a transparent, rigid support, a polarizing iilm amxed thereto, a transparent barrier film affixed to the opposite face of said polarizing iilm, and a relatively heavy adhesive layer comprising a polymerized, incomplete vinyl acetal resin affixed to and positioned intermediate said barrier layer and a second transparent, rigid support, said polarizing film adhering directly and permanently to said firstmentioned rigid support, all of the elements of said combination being permanently bonded together to provide a substantially shatterproof structure.

9. In combination, a transparent, rigid support, a polarizing film aflixed thereto, a transparent barrier iilm affixed to the opposite face of said polarizing film, and a relatively heavy adhesive layer comprising a plasticlzed, polymerlzed, incomplete vinyl acetal resin afxed to and positioned intermediate said barrier layer and a second transparent, rigid support, said polarizing iilm adhering directly and permanent ly to said first-mentioned rigid support, all of the elements of said combination being permanently bonded together to provide a substantially shatterproof structure.

10. A lamination comprising a glass sheet, a polarizing lm comprising a suspension of orlented polarizing particles in a sheet of a polymerized incomplete vinyl acetal resin directly aflixed to and in contact with one surface thereof, a transparent membrane amxed to and over- ,lying said polarizing iilm, a plasticlzed polymerized incomplete vinyl acetal resin overlying and aiiixed to said membrane, and a second glass sheet overlying and aiiixed to said resin, saidl a polarizing film comprising a suspension of polarizing crystals in a polymerized incomplete vinyl acetal resin intermediate said regenerated cellulose layer and the second glass sheet and adherent to both said cellulose layer and said second glass sheet.

12. The process of forming a lamination comprising applying a thin lm of a suspension of oriented polarizing particles in a polymerized incomplete vinyl .acetal resin to a transparent membrane, applying said membrane and film to a glass plate with the film between the membrane and plate, covering the exposed surface of the membrane with a plasticlzed polymerized incomplete vinyl acetal resin, covering the resin with a second glass plate and pressing the assemblage to effect a permanent bond between said plasticlzed resin and said second glass plate and between said plasticized resin and said membrane.

EDWIN H. LAND. 

